[SOLVED]820-3437 board no back light

[turbo]

820-3437 board no back light , there was slight water damage , no back light, there shot to ground on u7701 and fuse was blown , board cleaned now , changed the fuse and u7701, not the shot to ground is gone , still no back light ,

after connecting screen i get 8.59v on L7701, the voltage should be way higher... any idea ... is still u7701 or something else , thanks

 

[aprendiz]

Check feedback trace....

 

[turbo]

ya FB trace was gone just fixed it , now getting 39v, c8317 , still no back light ,

 

[aprendiz]

bad connector or bad cable.......

 

[turbo]

i already changed the connector , even thou the original connector was looking really good, also tested the screen with another mac it work perfect,


any iidea?? im getting no load 39v.... in c8317, connector good, lcd good ....

 

[larossmann]

do you get 39v at pins 3/4 of the LCD connector itself? 39v means it is being made, but it isn't getting to the LCD.

 

[turbo]

do you get 39v at pins 3/4 of the LCD connector itself? 39v means it is being made, but it isn't getting to the LCD.

yes the 3/4 connector has 39v... also new connector , i chk the lcd with different board it light up ...

 

[turbo]

also old connector was looking good b4 change ,

 

[turbo]

backlight return r7727-22 has arounf 18-19v

 

[dukefawks]

PWM and EN signal present? The return lines should not be that high.

 

[turbo]

EN signal is there, PWM should i chk with lcd connected ?

 

[larossmann]

Yes, LCD connected.

 

[turbo]

SOLVEDDDDDDDDDDD.....any guess what was the problem? i was getting 39v on pin, also new connector , lcd was good but no back light ........you

guess then ill tell what was wrong ..feels so good )))

 

[dukefawks]

Backlight flat cable was not plugged in or upside down inside the LCD.

 

[turbo]

Backlight flat cable was not plugged in or upside down inside the LCD.

lol no , i would never do that ..

the board had water damage, u7701 had shot to ground , also feed back trace from diod to A5 was missing too,

i put the new chip , fix the trace , i was getting 39v out put, still no back light , then some one told me to change the connector , so i did change the connector still no back light ...


THE PROBLEM WAS IN THE U7701, ALL BALL WAS NOT CONNECTING, all i had to do reflow properly(u7701)...

when duke said retune line shouldn't be that high(19v) ...... that mean 39v going throu all led strip and coming back on retune line 18v. (inside registance lowering the voltage 39 to 19v).. that mean from chip side no ground output..... or load 39v , im not too good with writing ...i think you understand the point ....


so after reflowing my chip its work like chump!!!!

and i think duke is superb! real good engineer ......

thank you all for help